Threaded parts are subject to various errors during forming including errors in the thread flank angle and flank shape, and lead errors. In addition, there is an unavoidable clearance between thread connected parts so that the pitch diameter of the nut and male thread are not the same. On threads having angled flanks such as the commonly used 60 degree flank angle, the thread clearance can allow a lock nut to tilt or cock relative to the spindle or shaft and cause an end face on the lock nut to be out of square with the axis of the spindle or shaft. An out of square end face on the lock nut can cause deformation of the spindle or shaft by off-center forces and or uneven bearing preload.
Various different lock nuts have heretofore been made. Some lock nuts such as disclosed in U.S. Pat. Nos. 4,086,946 and 5,454,674, press inserts or weakened thread sections of the lock nut radially inwardly against the threads on the spindle. These lock nuts only provide locking engagement of the lock nut to the spindle or shaft at circumferentially spaced locations and do not eliminate thread clearance evenly around the entire circumference. U.S. Pat. No. 4,557,652, discloses a lock nut having two separate annular members that are interconnected by elastomeric plugs or a elastomeric ring and the two members can be foceably separated by screws threadly mounted in one of the members for adjustment parallel to the axis of the member, to separate the members for locking. Pins are provided to slidably and non-rotatably interconnect the two members, but some relative angular movement can occur due to necessary clearances between parts.
Adjustable lock nuts have also been made in one piece with one internal and one external groove dividing the lock nut into a load carrying section and a locking section, and a thin intermediate section that integrally connects the load carrying section and the locking section. As disclosed in U.S. Pat. No. 4,043,692 (FIGS. 5), the locking section is adapted to be drawn toward the load carrying section by bolts paralleling the axis of the lock nut and threaded into the load carrying section. However, such lock nuts cannot be used in applications where there is insufficient clearance at the end of the lock nut to enable access to the adjusting bolts with a suitable wrench.